API replacement for recently removed BinaryenRemoveImport

With BinaryenRemoveImport respectively Module#removeImport removed, there is no way currently to remove a memory or table import via the C- and JS-API while still keeping the memory intact otherwise. While this isn't super important, I used that for example in one asm.js test where there can't be a memory import, while otherwise emitting the same module.

If I understood correctly, what's necessary to remove an import is to unset module and base on a supported element, but I wonder what'd be the best way to implement this API-wise. If we'd use the internal name, there might be a memory, a table and a function all using name 0 for example. If we'd use the external name, we might end up having functions with no body that were previously imported. Any suggestions?

Start by reviewing the removal of BinaryenRemoveImport and Module#removeImport in the linked pull request, then inspect the C- and JS-API entry points mentioned in the issue. Check the asm.js test example that previously used import removal. Done means a decided API design can remove a memory or table import while preserving the element and is covered for both APIs.